Public Missiles - Quantum Leap

Contributed by Mike Murphy

Construction Rating: starstarstarstarstar_border
Flight Rating: starstarstarstarstar
Overall Rating: starstarstarstarstar_border
Manufacturer: Public Missiles
PML Quantum Leap

Brief:
This is a custom manufacturer modification of the two stage Quantum Leap 3000 with Public Missiles Close Proximity Recovery (CPR) two stage drogue to main recovery system. Modifications included adding ten inches to both the booster and sustainer in order to accommodate longer motors. I also had the kit shipped with PML's fiberglass tubes.

Construction:
The much awaited box arrived only six days after I ordered it (and just in time for Christmas!) from PML after much soul searching on exactly what I wanted from the kit. The large box was well packed as usual for PML kits and all the parts were contained in the standard plastic bag except for the motor and body tubes. I have a PML AMRAAM 4.0 and built it with the Kwik-Switch (KS) motor mount system and have disliked that particular component from the start. The of the KS is excellent but since I fly in the Southern California desert with practically unlimited space, the limit of 13.75 inches of motor length is somewhat er...well, limiting! Having learned that lesson and having the typical craving to put yet more motor in each of my projects, I ordered the kit with extended body tubes for the booster and sustainer and corresponding longer motor mount tubes. Also in order to be able to launch the rocket more than once I ordered the kit with PML's fiberglassed tubing and upgraded the standard .062 G-10 fins to .125 G-10. As you can see from the photos there were over 135 parts total to assemble but there are no major issues to be overcome. As with all PML kits, the rocket uses pistons for drogue and main deployment. Quality overall was excellent and the fiberglassing was phenomenal. Believe it when they say all you have to do is prime and paint. The nose cone was the typical excellent quality blow molded PML cone. In order to accommodate the extra weight of the fiberglass tubes and extra length, I upgraded the main and booster chutes to 54" and 48" respectively.

PML Quantum Leap

The instruction booklet was outstanding with plenty of illustrations and clear steps in logical order. Since the body tubes were glassed with two wraps of six ounce cloth, the nosecone didn't match the outer diameter of the rocket. To make a nice transition I put a one inch wrap of fiberglass followed by a two inch wide wrap which increased the diameter to the correct size. There were the typical blow molding marks that had to be sanded out of the nose cone and then I put a coat of finishing epoxy over the whole thing making for a nice smooth finish that painted up nicely. I have had trouble sometimes with paint not sticking to plastic nosecones so now I put a coat of finish epoxy on all of my nose cones making it easy to get a nice smooth finish that the paint sticks to quite well.

The body tubes were absolutely bullet proof and exceptional as they have the best fiberglassing I've ever seen. Construction of the booster is straightforward with no difficulties. The booster uses motor ejection for the recovery system with a piston which negates the need for wadding. With the piston in place, the space for the booster recovery components is tight but does accommodate the 48 inch parachute and tubular nylon shock cord.

Staging is accomplished via PML's interstage coupler. Basically it consists of a 38mm mounting tube for the timer, a 3 inch section of fiberglassed body tube, a coupler, and a bulkplate (see PML's website for photos and a line diagram of the exact configuration). The upper section of the coupler fits into the base of the sustainer with the staging timer remaining with the booster section at separation. I fiberglassed the inside of all the couplers since I want to fly this bird with some larger motors.

The sustainer is a little different on construction due to the method of staging. Approximately three inches of the interstage coupler slides into the bottom of the sustainer which means that much of the sustainer fins are not attached to the motor tube. To overcome this weakness, pre-cut fiberglass is supplied to reinforce the fins which worked out so well I fiberglassed the booster fins in the same manner for strength.

PML Quantum Leap The only problem I have with PML's CPR deployment system is the 38mm altimeter tube that ends up being the weakest link in the entire rocket. In the last year I've broken two of them (one on this rocket when the motor CATOed on the first flight and one on my 4 inch AMRAAM.) PML graciously replaced the one on the AMRAAM for free but I opted to go with the Hawk Mountain G-10 CPR upgrade which is far superior in strength. The 38mm phenolic tube is somewhat brittle and prone to break when the rocket is flexed (as in recovery or if the bird lands horizontal after a motor CATO.) This isn't a major issue as it is strong enough most of the time but I like my rockets to be bulletproof. This is the only issue that kept me from giving the kit a 5 on construction.

PML Quantum LeapPML Quantum Leap

Aiming for the bulletproof rating, I filled the fin cans on both the booster and sustainer with PML's two part expanding foam using several pours each. I had to make paper funnels since there wasn't much room between the motor tube and the body tube and I wanted to minimize the mess. It worked out quite well and I highly recommend this product since I can literally stand on the tubes. The sustainer survived a motor CATO without damage to the fin can. The motor shooting up through the rocket was another story however--it went through the sustainer motor bulkhead, destroyed the piston, and shot the upper half of the rocket over 50 feet in the air. Other than the internal damage, the body tubes didn't even have a scratch! Those PML fiberglass tubes really are bulletproof! The altimeter tube fractured when it landed on its side, hence my gripe about using phenolic tubing when G-10 tubing would have survived.

Overall, construction is straightforward and no special techniques other than the internal fiberglassing of the fins are required. With the exception of the phenolic tube in the CPR this is a great kit and highly recommended.

Finishing:
Again, the fiberglassing by PML was outstanding. After filling the weave of the fiberglass used to reinforce the fins, I primed and painted the rocket with good old Rustoleum products. I opted for dark blue with a yellow nose cone and roll markings.

Construction Rating: 4 out of 5

Flight:
I prepared the first flight as a single stage to verify the electronic recovery. Flight preparation with the CPR is very easy. Attach ematches to the connectors, add 1/2 gram black powder to the built-in ejection cups, add a little wadding to keep the powder on the ematch and put the vinyl cap on the charge cylinder. Attach the switch leads and insert into the CPR altimeter tube. Screw the rocket halves together and it's done. All in all it takes about 15 minutes to prepare the rocket for a single stage flight. I built a Dr. Rocket 38/600 with an I-366R, and put it on the pad. 5, 4, 3, 2, 1, BOOM. The motor CATOed and half the rocket shot about 50 feet in the air. The altimeter tube fractured when it landed on the desert floor. The motor casing failed at the rear threads, shooting the motor forward through the bulkplate at the top of the motor section, through the piston and shooting the upper half of the rocket into the air. Repairs were made over the next couple of weeks and then it was time to try again.

Next flight was with a Cesaroni I540. The motor chuffed (apparently Cesaroni left the igniter pellet out of the first batch of I540's), causing the rocket to sit there for a few seconds burning before finally pressurizing and then with a roar sent the upper stage to 2753 feet. Drogue deployment was right after apogee and main deployment at 600 feet just like planned. I only had a 100 yard walk to recover the first successful flight.

Emboldened by the success I put a Cesaroni J210 in the sustainer stage (another single stage flight due to increasing winds) and the rocket made it to 3991 feet.

Finally the winds died down a bit and I decided to go for it. Preparing for a two stage flight is a bit more complicated. The upper stage is prepared as before. The igniter is inserted into the sustainer during assembly and the igniter leads threaded through the interstage coupler and attached to the timer. The stages are mated and after assembling the booster motor and inserting it into the booster. Since the rocket ended up over 9 feet long, mating the stages is a two person process.

For the first two stage flight I chose an I540 for the booster (the rocket is on the heavy side so I wanted plenty of grunt to get it off the pad) and a J280 Smokey Sam for the sustainer. Not wanting to push my luck too far I opted for only a one second delay between burnout and sustainer ignition with a ten second delay to deploy the booster parachute.

5,4,3,2,1, ignition! A perfectly straight boost under the I540, short delay, and the sustainer successfully ignited. Totally awesome flight to 6145 feet and a perfect recovery only about 500 yards from the launch rail.

I can't wait until next month, when I plan on launching a K445 staging to an L730.

Recovery:
Recovery is quick with the 54 inch parachute but with the fiberglass reinforcement, this is an asset. PML parachutes are top quality and I wouldn't change a thing.

Flight Rating: 5 out of 5

Summary:
The Quantum Leap is a top quality, well designed kit. The only think I would change would be replacing the 38mm phenolic altimeter tube, as it is a structural part in this design, with a G-10 altimeter tube to make the CPR mount one of the stronger parts of the rocket rather than the weakest link.

Overall Rating: 4 out of 5

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